A combined chemical, metabolic, and morphologic study of glial cells and myelin will yield new knowledge which is essential to our understanding of the myelination and demyelination processes. The highly specific and sensitive immunohistologic and quantitative immunoradiometric methods which we have developed for nervous system antigens (glial fibrillary acidic (GFA) protein and myelin basic protein) now permit a combined morphologic, chemical, and biochemical study. The correlated morphologic and chemical study of gliogenesis and myelination of the rat optic nerve may add further information about the chronological sequence and interrelationship of astrocytes and oligodendrocytes in normal processes of development, gliofibrillogenesis, myelin formation and myelin maintenance in the mammalian CNS. The experimental Wallerian degeneration study of the rat optic nerve will further elucidate the process of pathologic reactive gliosis which accompanies Wallerian degeneration in this model. These studies should help provide a further understanding of gliofibrillogenesis and myelination during development and reactive gliofibrillogenesis in Wallerian degeneration of the CNS. Isotopic labelling experiments should provide new insight on the relationship and function of the GFA protein to glial filaments within astrocytes during development and gliofibrillogenesis.